The invention, as originally conceived, pertains to a method and means for therapeutically and/or prophylactically dealing with a thrombotic or with a potentially thrombotic condition in a human limb, particularly in a leg. Such thrombotic conditions generally occur in the deep veins, hence, the term deep-vein thrombosis, herein abbreviated to DVT. The literature.sup.1 is beginning to accumulate important evidence of the successful use of a so-called foot pump in reducing the chances of thrombo-embolism, following surgery wherein a blood clot in the venous system may otherwise have proven fatal. By foot-pump use is meant methods and means as disclosed and discussed in U.S. Patent Nos. Re. 32,939, Re. 32,940, 4,696,289, and 4,721,101. In the present specification, the disclosures of these patents are incorporated by reference. FNT .sup.1 See, for example, Stranks/MacKenzie/Grover/Fail, "The A-V Impulse System Reduces Deep-Vein Thrombosis and Swelling after Hemiarthroplasty for Hip Fracture"; Journal of Bone Joint Surgery (British), Vol. 74-B, No. 5, September 1992, pp. 775-778, including references cited therein; and see also Bradley/Krugener/Jager, "The Effectiveness of Intermittent Plantar Venous Compression in Prevention of Deep Venous Thrombosis after Total Hip Arthroplasty", The Journal of Arthroplasty, Vol. 8, No. 1, 1993.
It suffices for present purposes to state that a foot-pump appliance of the character indicated makes use of a Gardner/Fox discovery reported in 1983 ("The Venous Pump of the Human Foot-Preliminary Report", Bristol Medico-Chirurgical Journal; Gardner and Fox; pp. 109-112; July 1983), namely that plantar veins of the foot provide a pool of blood for return via the venous system, and that in unafflicted persons, the transfer of weight-bearing from one to the other foot in the course of walking entails a transient stretching of plantar veins and thus a transient shrinking of plantar-vein capacity, such as to drive venous flow back to the heart via the check-valve action of the veins. Significantly, no muscular action is involved in this venous-return flow. The foot-pump disclosures of said patents provide the patient who is bed-ridden or otherwise unable to walk with a mechanical substitute for the intermittent weight-bearing action available to ambulatory individuals. The mechanical substitute involves periodic application of a relatively short pulse of compression against the underside of the foot, between the ball and the heel of the foot, to a degree sufficient to transiently reduce the volume of the plantar veins, thus driving an increment of venous return flow back to the heart, primarily via the deep veins of the leg.
In the circumstance of using the mechanical foot pump to deal with a thrombotic condition in the leg, the deep veins will have been partially or wholly blocked by a developing or a developed clot accumulation, so that deep-vein resistance to stimulated flow compels superficial veins to assume an abnormal flow, for each foot-pump stimulation. This can be the source of increased pain and may result in a long-term abnormal reliance upon the superficial veins. Moreover, in the event that a thrombolitic agent, such as streptokinase, has been introduced into the circulatory system for purposes of dissolving the clotted condition, any diversion of venous-return flow to superficial veins is a by-passing of the deep-vein target of therapy; this can be interpreted to mean that an unnecessarily great proportion of thrombolitic agent must be introduced or that the time of therapeutic treatment may be longer than necessary, were it possible to more effectively focus delivery of the thrombolitic agent at the deep-vein situs of thrombosis.